This invention relates to modifying conventional glass or plastic windows by combining such windows with a switchable glazing such as an SPD film or an SPD light valve or with a non-switchable device such as a tinted window or screen in a simple, novel and cost effective manner, and to the retrofitted windows produced thereby.
Light valves have been in use for more than sixty years for the modulation of light. As used herein, a light valve is defined as a cell formed of two walls that are spaced apart by a small distance, at least one wall being transparent, the walls having electrodes thereon, usually in the form of transparent, electrically conductive coatings. The cell contains a light-modulating element (sometimes herein referred to as an xe2x80x9cactivatable materialxe2x80x9d), which may be either a liquid suspension of particles, or a plastic film in which droplets of a liquid suspension of particles are distributed.
The liquid suspension (sometimes herein referred to as xe2x80x9ca liquid light valve suspensionxe2x80x9d or xe2x80x9ca light valve suspensionxe2x80x9d) comprises small, anisometrically shaped particles suspended in a liquid suspending medium. In the absence of an applied electrical field, the particles in the liquid suspension assume random positions due to Brownian movement, and hence a beam of light passing into the cell is reflected, transmitted or absorbed, depending upon the cell structure, the nature and concentration of the particles, and the energy content of the light. The light valve is thus relatively dark in the OFF state. However, when an electric field is applied through the liquid light valve suspension in the light valve, the particles become aligned and for many suspensions most of the light can pass through the cell. The light valve is thus relatively transparent in the ON state. Light valves of the type described herein are also known as xe2x80x9csuspended particle devicesxe2x80x9d or xe2x80x9cSPDs.xe2x80x9d
Light valves have been proposed for use in numerous applications including, e.g., alphanumeric and graphic displays; television displays; filters for lamps, cameras, optical fibers, and windows, sunroofs, sunvisors, eyeglasses, goggles and mirrors and the like, to control the amount of light passing therethrough or reflected therefrom as the case may be. As used herein the term xe2x80x9clightxe2x80x9d generally refers to visible electromagnetic radiation, but where applicable, xe2x80x9clightxe2x80x9d can also comprise other types of electromagnetic radiation such as, but not limited to, infrared radiation.
For many applications, as would be well understood in the art it is preferable for the activatable material, i.e., the light modulating element, to be a plastic film rather than a liquid suspension. For example, in a light valve used as a variable light transmission window, a plastic film, in which droplets of liquid suspension are distributed, is preferable to a liquid suspension alone because hydrostatic pressure effects, e.g., bulging, associated with a high column of liquid suspension, can be avoided through use of a film, and the risk of possible leakage can also be avoided. Another advantage of using a plastic film is that in a plastic film, the particles are generally present only within very small droplets, and hence do not noticeably agglomerate when the film is repeatedly activated with a voltage.
As used herein, the terms xe2x80x9cSPD filmxe2x80x9d or xe2x80x9clight valve filmxe2x80x9d mean at least one film or sheet comprising a suspension of particles used or intended for use by itself or as part of a light valve. The light valve film or SPD film comprises either: (a) a suspension of particles dispersed throughout a continuous liquid phase enclosed within one or more rigid or flexible solid films or sheets, or (b) a discontinuous phase of a liquid comprising dispersed particles, the discontinuous phase being dispersed throughout a continuous phase of a rigid or flexible solid film or sheet. The light valve film or SPD film may also comprise one or more other layers such as, without limitation, a film, coating or sheet, or combination thereof, which may provide the light valve film or SPD film with (1) scratch resistance (2) protection from ultraviolet radiation (3) reflection of infrared energy, and/or (4) electrical conductivity for transmitting an applied electric or magnetic field to the activatable material.
U.S. Pat. No. 5,409,734 exemplifies a type of light valve film that is formed by phase separation from a homogeneous solution. Light valve films made by cross-linking emulsions are also known. Examples of these are described in U.S. Pat. Nos. 5,463,491 and 5,463,492, both of which are assigned to the assignee of the present invention.
The following is a brief description of liquid light valve suspensions known in the art which are useful in forming windows retrofitted with a switchable glazing, although the invention is not limited to the use of only such suspensions, nor is it limited to the use of switchable glazings per se since alternate classes of light modulating devices, (e.g., non-switchable devices) as described below, can be used in place of such switchable window enhancements.
1. Liquid Suspending Media and Stabilizers
A liquid light valve suspension for use with the invention may be any liquid light valve suspension known in the art and may be formulated according to techniques well known to one skilled in the art. The term xe2x80x9cliquid light valve suspensionxe2x80x9d, as used herein, means a xe2x80x9cliquid suspending mediumxe2x80x9d in which a plurality of small particles is dispersed. The xe2x80x9cliquid suspending mediumxe2x80x9d comprises one or more non-aqueous, electrically resistive liquids in which there is preferably dissolved at least one type of polymeric stabilizer, which acts to reduce the tendency of the particles to agglomerate and to keep them dispersed and in suspension.
Liquid light valve suspensions useful in the present invention may include any of the liquid suspending media previously proposed for use in light valves for suspending the particles. Liquid suspending media known in the art which are useful herein include, but are not limited to the liquid suspending media disclosed in U.S. Pat. Nos. 4,247,175 and 4,407,565. In general, at least one of the liquid suspending medium and the polymeric stabilizer dissolved therein is chosen in a manner known in the art so as to maintain the suspended particles in gravitational equilibrium.
The polymeric stabilizer, when employed, can be a single solid polymer that bonds to the surface of the particles, but which also dissolves in the non-aqueous liquid or liquids of the liquid suspending medium. Alternatively, two or more solid polymeric stabilizers may serve as a polymeric stabilizer system. For example, the particles can be coated with a first type of solid polymeric stabilizer such as nitrocellulose which, in effect, provides a plain surface coating for the particles, after which they are re-coated with one or more additional types of solid polymeric stabilizer that bond to or associate with the first type of solid polymeric stabilizer and which also dissolves in the liquid suspending medium to provide dispersion and steric protection for the particles. Also, liquid polymeric stabilizers may be used to advantage, especially in SPD light valve films, as described in U.S. Pat. No. 5,463,492.
2. Particles
Inorganic and organic particles may be incorporated into a light valve suspension useful in forming a switchable enhancement for use in retrofitting a window in accordance with the present invention. Such particles may be either light-absorbing or light-reflecting in the visible portion of the electromagnetic spectrum. For some particular applications the particles can be reflective at infrared wavelengths.
Conventional SPD light valves have generally employed polyhalide particles of colloidal size, that is the particles generally have a largest dimension averaging about 1 micron or less. As used herein, the term xe2x80x9ccolloidalxe2x80x9d, when referring to particle size, shall have the meaning given in the preceding sentence. Preferably, most polyhalide or other particles used or intended for use in an SPD light valve suspension used in accordance with the invention will have a largest dimension which averages less than one-half of the wavelength of blue light, i.e., less than 2000 Angstroms, to keep light scatter extremely low. As used herein, the term xe2x80x9canisometricxe2x80x9d, which refers to particle shape, means that at least one dimension is larger than another. Typically, anisometric particles (sometimes referred to as particles which are anisometrically shaped), are desirable in an SPD light valve suspension so that the particles will block less light when the suspension is activated than when it is unactivated. For some suspensions the reverse is true, however. Desirable anisometric shapes for the particles include, without limitation thereto, particles shaped like rods, cylinders, plates, needles, blades, prisms, and other shapes known in the art.
A detailed review of prior art polyhalide particles is found in xe2x80x9cThe Optical Properties and Structure of Polyiodidesxe2x80x9d by D. A. Godina and G. P. Faerman, published in xe2x80x9cThe Journal of General Chemistryxe2x80x9d, U.S.S.R. Vol. 20, pp. 1005-1016 (1950).
Herapathite, for example, is defined as a quinine bisulfate polyiodide, and its formula is given under the heading xe2x80x9cquinine iodsulfatexe2x80x9d as 4C20H24N2O2.3H2SO4.2HI.I4.6H2O in The Merck Index, 10th Ed. (Merck and Co., Inc., Rahway, N.J.). In polyiodide compounds, the iodide anion is thought to form chains and the compounds are strong light polarizers. See U.S. Pat. No. 4,877,313 and Teitelbaum et al. JACS 100 1978), pp. 3215-3217. The term xe2x80x9cpolyhalidexe2x80x9d is used herein to mean a compound such as a polyiodide, but wherein at least some of the iodide anion may be replaced by another halide anion. More recently, improved polyhalide particles for use in light valves have been proposed in U.S. Pat. Nos. 4,877,313, 5,002,701, 5,093,041 and 5,516,463. These xe2x80x9cpolyhalide particlesxe2x80x9d are formed by reacting organic compounds, usually containing nitrogen, with elemental iodine and a hydrohalide acid or an ammonium halide, alkali metal halide or alkaline earth metal halide.
For some applications, however, it may be desirable to use non-polyhalide particles in light valve suspensions and films, especially where the stability of the material composing the particles is known to be excellent.
Regardless of the type of window enhancement, such as an SPD film or SPD light valve, which is involved, it is desirable to have a convenient and cost-effective method of combining the enhancement with a conventional, i.e., unenhanced, window in order to provide improved performance beyond that of the conventional window alone. Windows have frequently been retrofitted in the prior art on their outside, i.e., exterior, surfaces with plastic films that, for example, reflect infrared heat or make the window breakage resistant, by directly laminating the plastic film to the viewing area of the window with an adhesive. Such arrangements present technical difficulties, however, such as avoiding wrinkles or trapped air bubbles or solvent between the film and the window. The present invention offers a convenient alternative by substantially avoiding such direct lamination to most or all of the viewing area of the window, by instead securing the window enhancement or switchable glazing to (a) the window frame, or (b) a small area on the viewing area of the window at or near the edge or edges of the window via securing means in a manner so as to produce a narrow xe2x80x9cgapxe2x80x9d between the enhancement and the window at those portions of the enhancement not in contact with the securing means. The modification of a conventional window by combining the window in some manner with a window enhancement, i.e., a switchable glazing or non-switchable light modulating device, is referred to herein as xe2x80x9cretrofittingxe2x80x9d the conventional window.
The terms xe2x80x9cwindowxe2x80x9d and xe2x80x9cconventional windowxe2x80x9d as used herein include both glass and plastic windows, and combinations thereof, with any number of panes, i.e., single-pane and multi-pane, e.g., double-glazing, windows of any composition, size and shape, whether or not tinted, including both the window viewing area and frame, and for all uses such as, but not limited to, windows used in architectural and automotive vehicle applications, as well as windows used in various other transportation vehicles such as, boats, trains, aircraft, spacecraft and space stations, and windows used in greenhouses.
It should be further understood that, although not part of the present invention, one could arrange to place a separate (not physically combined) window enhancement such as an SPD film or SPD light valve in series with a window. For example, in a building, one could affix the frame of an SPD light valve to the wall of the building so that the light valve and window were in series. If hinges were used, it would be possible to place the light valve in front of the window, or swing it out of that position, as desired. However, such arrangements where the enhancement is separate from the window, i.e., not physically combined to some extent, are not deemed retrofitting as that term is used herein and are thus not considered as forming a part of the present invention.
As indicated above, therefore, the present invention is directed to methods for retrofitting a xe2x80x9cconventionalxe2x80x9d window with switchable and non-switchable window enhancements. The invention is further directed to the improved retrofitted windows produced by the method, i.e., improved in that they avoid the technical difficulties (wrinkles, trapped air and/or solvent bubbles, etc.) as discussed above.
In a first embodiment, the invention is directed to a method for retrofitting a window by physically combining the window with a window enhancement, as that term is defined herein. The method includes providing a window comprising at least a relatively transparent viewing pane with first and second opposed viewing surfaces; providing at least one means for mounting the enhancement (described below) for securing the window enhancement to the window; and securing the window enhancement to the window with the at least one mounting means in a manner wherein the enhancement overlies at least a portion of the viewing pane.
The mounting means is adapted such that upon its use in mounting the enhancement, a gap is produced between the enhancement and the window in those areas where the enhancement is not in contact with the mounting means. The existence of the gap thus prevents problems such as wrinkling and/or entrapment of liquids. The gap may, if desired, be at least partially filled with air or some inert gas, or alternately the air may be at least partially evacuated from the gap, thus producing an at least partial vacuum condition between the window and the enhancement.
In one embodiment of the invention, the at least one mounting means may be installed on the viewing pane portion of the window. One may choose, for example, to position the mounting means along two opposed edge portions on one viewing surface of the pane, e.g., at the top and the bottom of the window pane, or along the left and the right sides thereof. Alternately, if desired, the enhancement can be mounted, for example, on a plurality of mounting means located, e.g., at the top, the bottom and one or more of the longitudinal side edges of the viewing pane.
In a further embodiment, the enhancement may first be laminated, directly or indirectly, to a relatively rigid substrate formed, e.g., of glass or a plastic, with the resultant laminate thereafter being secured to the viewing pane with the use of the mounting means.
Window enhancements chosen for use with the present invention may comprise, e.g., a switchable glazing such as an SPD film, an SPD light valve, an electrochromic film or window or a liquid crystal film or window. In alternate applications, however, the window enhancement used in the method of the invention may comprise a non-switchable light modulating device, such as a tinted window or screen, a solar control film, an impact resistant film or a flexible or rigid panel.
In a further alternate embodiment of the invention, the mounting means may initially be mounted directly upon the enhancement which then, in turn, is secured to the window by the use of such means.
The window may further comprise a frame portion configured and adapted to support the viewing pane. The frame typically comprises a top member, a bottom member, and first and second longitudinal side members, wherein the side members are connected, at opposite ends thereof, to the top and bottom members to form the frame portion. If desired, the enhancement may be secured upon the window frame portion instead of, or in addition to securing it to the window viewing pane. When securing the embodiment to the frame portion, the mounting means may be positioned at a variety of locations, i.e., on the top and bottom frame members, or at the left and right longitudinal sides of the frame or, if desired, on all four of the members which comprise the frame portion. Notwithstanding whether the mounting means are positioned upon the viewing pane or the frame portion however, a gap, as described above, is produced between the enhancement and the window due to the mounting means, which gap overcomes the deficiencies noted in the prior art. As with the embodiment described above, the gap may be at least partially filled with a gas (e.g., air or some inert gas) or at least partially evacuated.
In another embodiment of the invention, at least one projecting spacer member (and preferably a plurality of such members) may be provided between the enhancement and the window, in the gap therebetween, which spacer member(s) are sized and configured to maintain the gap at a predetermined width, i.e., to prevent sagging of the enhancement towards the surface of the window.
In an alternate embodiment of the invention, the mounting means may be positioned at corresponding locations upon both the window and the window enhancement. Thus, the width of the gap therebetween is increased to the thickness of two such means, positioned one above, i.e., atop, the other.
Mounting means useful in the present invention may be chosen from a variety of fastening and securing devices well known in the art. One preferred means for mounting the enhancement upon the window is through the use of one or more securing strips, i.e., swatches of a plastic or cloth material provided upon at least a portion of their outer surfaces with an adhesive material to permit securing them to, e.g., the viewing pane and/or the frame portion of a window, as well as to the surface of the window enhancement chosen for mounting upon the window. Alternate mounting means may include, but are not limited to, a variety of fastening devices such as screws, nails, bolts, snaps, rivets, staples, magnetized metal bars and the like. Some such alternate means, i.e., such as screws, bolts and the like may be provided with a spacer member, i.e., a washer or an o-ring, to assist in maintaining the gap between the window and the enhancement. These alternate fasteners are preferred for use when the enhancement is to be mounted upon the frame portion of the window, i.e., and not the viewing pane, since driving, e.g., a screw or rivet, into a glass viewing pane to mount the enhancement would likely damage or perhaps destroy the pane. Such would not be the case, however, in the case of plastic panes and thus such alternate mounting means may be used on window panes comprised of plastic.
It is, moreover, desirable, although not required, that, when adhesive-backed securing strips are used as the mounting means, the window be cleaned by substantially removing any dust or dirt therefrom prior to mounting the securing strips, to enhance the adhesion of the strips. The strips are typically provided with an adhesive material on at least one surface thereof to facilitate bonding, i.e., to the window and/or to the enhancement. The adhesive material may be selected, for example, from pressure sensitive adhesives and heat or radiation curable adhesives. The adhesive surface(s) may, if desired, be protected with a removable release paper, which is removed from the strip and discarded prior to application of the strip to the window and/or the enhancement.
In those embodiments which, as described above, utilize mounting means such as securing strips positioned at corresponding locations (e.g., face-to-face) upon both the window (the viewing pane or the frame) and the enhancement, such strips may, for example, comprise a fabric or plastic swatch that incorporates a magnetic material, such that the enhancement is at least partially secured to the window as a result of a magnetic attraction between corresponding ones of said strips. In an alternate embodiment, the strips may instead include hook and loop (e.g., Velcro(copyright) brand) fastener arrangements whereupon the enhancement is mounted to the window due to interengagement of the hooks and the loops on corresponding ones of the securing strips.
If desired, either the window enhancement or the viewing pane portion of the window, may be provided with a coating, such as an anti-reflective coating, or some form of protectant coating, which is applied thereto in a manner well known in the art.
In a further embodiment of the invention, the window may comprise a plurality of viewing panes positioned in series and spaced apart, one from the other, due to their position within the window frame portion. In such an embodiment, the enhancement may be positioned adjacent an inner surface of one of the viewing panes, and secured either to the pane or alternately upon an abutting surface of the frame portion extending into the space between the viewing panes, wherein a first surface of the enhancement is separated from the window by the above-described gap formed due to the thickness of the mounting means, and the second, opposed surface of the enhancement is exposed to the space between the two adjacent panes. One particular example of the above-described arrangement is a double pane or so-called double-glazing window wherein the enhancement is applied to an inner surface of one of the viewing panes, i.e., one of the surfaces exposed to the space between the two viewing panes.
In still another embodiment, the invention comprises a method for retrofitting a multi-pane window with a window enhancement. The method involves providing a window comprising a frame portion together with a plurality of relatively transparent viewing panes positioned in series within the frame, with the frame being configured and adapted to support the viewing panes and to separate them one from another by maintaining a space between adjacent panes. The method further includes providing at least one window enhancement selected from among switchable and non-switchable window enhancements for combining with the window; and securing, with the use of the above-described securing means, a window enhancement upon at least a portion of at least one of the viewing panes, on an inner surface of the pane separated by such space from the next adjacent pane. If desired, the enhancement may initially be laminated upon a supporting substrate, such as a sheet of plastic or glass, whereupon the resultant laminate is thereafter secured to the inside surface of the viewing pane with the use of the securing means. The window enhancement may comprise, e.g., a switchable glazing such as an SPD film, SPD light valve, an electrochromic film or window or a liquid crystal film or window. Alternately the enhancement may instead be a non-switchable light modulating device chosen from among, for example, a tinted window, a screen, a solar control film, impact resistant film or a flexible or rigid panel.
The invention is further directed to improved retrofitted windows produced by the method of the invention. One embodiment includes, in combination, a window retrofitted with a switchable or a non-switchable window enhancement, wherein the combination includes a window comprising a frame portion and at least one relatively transparent viewing pane, wherein the frame portion is adapted to secure and support the at least one pane in a desired orientation. The combination additionally comprises a window enhancement selected from the group including switchable and non-switchable window enhancements, wherein the enhancement is secured to the window with the use of at least one securing means; and at least one securing means for securing the window enhancement to the window, such that when the enhancement is in place upon the window a gap is produced between the enhancement and the window. When securing strips are used as the securing means each said securing strip comprises at least one surface provided with an adhesive component. Such strips may, if desired, be provided as well with an additional bonding component such as a magnetic material or a hook and loop fabric arrangement.
In a still further embodiment, the combination may additionally comprise a plurality of spacer members adapted to maintain the width of the gap between the window and the enhancement at a substantially constant dimension. These members may be installed upon the enhancement and project from the enhancement toward the window. Alternately, they may be installed upon the window, whereupon they project from the window toward the enhancement. In another embodiment of the retrofitted window produced according to the invention, the enhancement may initially be laminated to an underlying substrate formed, e.g., of a sheet of glass or plastic which is, in turn, secured to the window with the aid of the mounting means.